gpu/command_buffer/client/vertex_array_object_manager.cc - chromium/src - Git at Google

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "gpu/command_buffer/client/vertex_array_object_manager.h"

 #include <stddef.h>
 #include <stdint.h>

 #include "base/logging.h"
 #include "base/macros.h"
 #include "gpu/command_buffer/client/gles2_cmd_helper.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
 #include "gpu/command_buffer/common/gles2_cmd_utils.h"

 namespace gpu {
 namespace gles2 {

 static GLsizei RoundUpToMultipleOf4(GLsizei size) {
   return (size + 3) & ~3;
 }

 // This class tracks VertexAttribPointers and helps emulate client side buffers.
 //
 // The way client side buffers work is we shadow all the Vertex Attribs so we
 // know which ones are pointing to client side buffers.
 //
 // At Draw time, for any attribs pointing to client side buffers we copy them
 // to a special VBO and reset the actual vertex attrib pointers to point to this
 // VBO.
 //
 // This also means we have to catch calls to query those values so that when
 // an attrib is a client side buffer we pass the info back the user expects.

 class GLES2_IMPL_EXPORT VertexArrayObject {
  public:
   // Info about Vertex Attributes. This is used to track what the user currently
   // has bound on each Vertex Attribute so we can simulate client side buffers
   // at glDrawXXX time.
   class VertexAttrib {
    public:
     VertexAttrib()
         : enabled_(false),
           buffer_id_(0),
           size_(4),
           type_(GL_FLOAT),
           normalized_(GL_FALSE),
           pointer_(nullptr),
           gl_stride_(0),
           divisor_(0),
           integer_(GL_FALSE) {}

     bool enabled() const {
       return enabled_;
     }

     void set_enabled(bool enabled) {
       enabled_ = enabled;
     }

     GLuint buffer_id() const {
       return buffer_id_;
     }

     void set_buffer_id(GLuint id) {
       buffer_id_ = id;
     }

     GLenum type() const {
       return type_;
     }

     GLint size() const {
       return size_;
     }

     GLsizei stride() const {
       return gl_stride_;
     }

     GLboolean normalized() const {
       return normalized_;
     }

     const GLvoid* pointer() const {
       return pointer_;
     }

     bool IsClientSide() const {
       return buffer_id_ == 0;
     }

     GLuint divisor() const {
       return divisor_;
     }

     GLboolean integer() const {
       return integer_;
     }

     void SetInfo(
         GLuint buffer_id,
         GLint size,
         GLenum type,
         GLboolean normalized,
         GLsizei gl_stride,
         const GLvoid* pointer,
         GLboolean integer) {
       buffer_id_ = buffer_id;
       size_ = size;
       type_ = type;
       normalized_ = normalized;
       gl_stride_ = gl_stride;
       pointer_ = pointer;
       integer_ = integer;
     }

     void SetDivisor(GLuint divisor) {
       divisor_ = divisor;
     }

    private:
     // Whether or not this attribute is enabled.
     bool enabled_;

     // The id of the buffer. 0 = client side buffer.
     GLuint buffer_id_;

     // Number of components (1, 2, 3, 4).
     GLint size_;

     // GL_BYTE, GL_FLOAT, etc. See glVertexAttribPointer.
     GLenum type_;

     // GL_TRUE or GL_FALSE
     GLboolean normalized_;

     // The pointer/offset into the buffer.
     const GLvoid* pointer_;

     // The stride that will be used to access the buffer. This is the bogus GL
     // stride where 0 = compute the stride based on size and type.
     GLsizei gl_stride_;

     // Divisor, for geometry instancing.
     GLuint divisor_;

     GLboolean integer_;
   };

   typedef std::vector<VertexAttrib> VertexAttribs;

   explicit VertexArrayObject(GLuint max_vertex_attribs);

   void UnbindBuffer(GLuint id);

   bool BindElementArray(GLuint id);

   bool HaveEnabledClientSideBuffers() const;

   void SetAttribEnable(GLuint index, bool enabled);

   void SetAttribPointer(
     GLuint buffer_id,
     GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride,
     const void* ptr, GLboolean integer);

   bool GetVertexAttrib(GLuint index, GLenum pname, uint32_t* param) const;

   void SetAttribDivisor(GLuint index, GLuint divisor);

   bool GetAttribPointer(GLuint index, GLenum pname, void** ptr) const;

   const VertexAttribs& vertex_attribs() const {
     return vertex_attribs_;
   }

   GLuint bound_element_array_buffer() const {
     return bound_element_array_buffer_id_;
   }

  private:
   const VertexAttrib* GetAttrib(GLuint index) const;

   int num_client_side_pointers_enabled_;

   // The currently bound element array buffer.
   GLuint bound_element_array_buffer_id_;

   VertexAttribs vertex_attribs_;

   DISALLOW_COPY_AND_ASSIGN(VertexArrayObject);
 };

 VertexArrayObject::VertexArrayObject(GLuint max_vertex_attribs)
     : num_client_side_pointers_enabled_(0),
       bound_element_array_buffer_id_(0) {
   vertex_attribs_.resize(max_vertex_attribs);
 }

 void VertexArrayObject::UnbindBuffer(GLuint id) {
   if (id == 0) {
     return;
   }
   for (size_t ii = 0; ii < vertex_attribs_.size(); ++ii) {
     VertexAttrib& attrib = vertex_attribs_[ii];
     if (attrib.buffer_id() == id) {
       attrib.set_buffer_id(0);
       if (attrib.enabled()) {
         ++num_client_side_pointers_enabled_;
       }
     }
   }
   if (bound_element_array_buffer_id_ == id) {
     bound_element_array_buffer_id_ = 0;
   }
 }

 bool VertexArrayObject::BindElementArray(GLuint id) {
   if (id == bound_element_array_buffer_id_) {
     return false;
   }
   bound_element_array_buffer_id_ = id;
   return true;
 }
 bool VertexArrayObject::HaveEnabledClientSideBuffers() const {
   return num_client_side_pointers_enabled_ > 0;
 }

 void VertexArrayObject::SetAttribEnable(GLuint index, bool enabled) {
   if (index < vertex_attribs_.size()) {
     VertexAttrib& attrib = vertex_attribs_[index];
     if (attrib.enabled() != enabled) {
       if (attrib.IsClientSide()) {
         num_client_side_pointers_enabled_ += enabled ? 1 : -1;
         DCHECK_GE(num_client_side_pointers_enabled_, 0);
       }
       attrib.set_enabled(enabled);
     }
   }
 }

 void VertexArrayObject::SetAttribPointer(
     GLuint buffer_id,
     GLuint index,
     GLint size,
     GLenum type,
     GLboolean normalized,
     GLsizei stride,
     const void* ptr,
     GLboolean integer) {
   if (index < vertex_attribs_.size()) {
     VertexAttrib& attrib = vertex_attribs_[index];
     if (attrib.IsClientSide() && attrib.enabled()) {
       --num_client_side_pointers_enabled_;
       DCHECK_GE(num_client_side_pointers_enabled_, 0);
     }

     attrib.SetInfo(buffer_id, size, type, normalized, stride, ptr, integer);

     if (attrib.IsClientSide() && attrib.enabled()) {
       ++num_client_side_pointers_enabled_;
     }
   }
 }

 bool VertexArrayObject::GetVertexAttrib(GLuint index,
                                         GLenum pname,
                                         uint32_t* param) const {
   const VertexAttrib* attrib = GetAttrib(index);
   if (!attrib) {
     return false;
   }

   switch (pname) {
     case GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING:
       *param = attrib->buffer_id();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_ENABLED:
       *param = attrib->enabled();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_SIZE:
       *param = attrib->size();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_STRIDE:
       *param = attrib->stride();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_TYPE:
       *param = attrib->type();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_NORMALIZED:
       *param = attrib->normalized();
       break;
     case GL_VERTEX_ATTRIB_ARRAY_INTEGER:
       *param = attrib->integer();
       break;
     default:
       return false;  // pass through to service side.
   }
   return true;
 }

 void VertexArrayObject::SetAttribDivisor(GLuint index, GLuint divisor) {
   if (index < vertex_attribs_.size()) {
     VertexAttrib& attrib = vertex_attribs_[index];
     attrib.SetDivisor(divisor);
   }
 }

 // Gets the Attrib pointer for an attrib but only if it's a client side
 // pointer. Returns true if it got the pointer.
 bool VertexArrayObject::GetAttribPointer(
     GLuint index, GLenum pname, void** ptr) const {
   const VertexAttrib* attrib = GetAttrib(index);
   if (attrib && pname == GL_VERTEX_ATTRIB_ARRAY_POINTER) {
     *ptr = const_cast<void*>(attrib->pointer());
     return true;
   }
   return false;
 }

 // Gets an attrib if it's in range and it's client side.
 const VertexArrayObject::VertexAttrib* VertexArrayObject::GetAttrib(
     GLuint index) const {
   if (index < vertex_attribs_.size()) {
     const VertexAttrib* attrib = &vertex_attribs_[index];
     return attrib;
   }
   return nullptr;
 }

 VertexArrayObjectManager::VertexArrayObjectManager(
     GLuint max_vertex_attribs,
     GLuint array_buffer_id,
     GLuint element_array_buffer_id,
     bool support_client_side_arrays)
     : max_vertex_attribs_(max_vertex_attribs),
       array_buffer_id_(array_buffer_id),
       array_buffer_size_(0),
       array_buffer_offset_(0),
       element_array_buffer_id_(element_array_buffer_id),
       element_array_buffer_size_(0),
       collection_buffer_size_(0),
       default_vertex_array_object_(new VertexArrayObject(max_vertex_attribs)),
       bound_vertex_array_object_(default_vertex_array_object_),
       support_client_side_arrays_(support_client_side_arrays) {
 }

 VertexArrayObjectManager::~VertexArrayObjectManager() {
   for (VertexArrayObjectMap::iterator it = vertex_array_objects_.begin();
        it != vertex_array_objects_.end(); ++it) {
     delete it->second;
   }
   delete default_vertex_array_object_;
 }

 bool VertexArrayObjectManager::IsReservedId(GLuint id) const {
   return (id != 0 &&
           (id == array_buffer_id_ || id == element_array_buffer_id_));
 }

 GLuint VertexArrayObjectManager::bound_element_array_buffer() const {
   return bound_vertex_array_object_->bound_element_array_buffer();
 }

 void VertexArrayObjectManager::UnbindBuffer(GLuint id) {
   bound_vertex_array_object_->UnbindBuffer(id);
 }

 bool VertexArrayObjectManager::BindElementArray(GLuint id) {
   return  bound_vertex_array_object_->BindElementArray(id);
 }

 void VertexArrayObjectManager::GenVertexArrays(
     GLsizei n, const GLuint* arrays) {
   DCHECK_GE(n, 0);
   for (GLsizei i = 0; i < n; ++i) {
     std::pair<VertexArrayObjectMap::iterator, bool> result =
         vertex_array_objects_.insert(std::make_pair(
             arrays[i], new VertexArrayObject(max_vertex_attribs_)));
     DCHECK(result.second);
   }
 }

 void VertexArrayObjectManager::DeleteVertexArrays(
     GLsizei n, const GLuint* arrays) {
   DCHECK_GE(n, 0);
   for (GLsizei i = 0; i < n; ++i) {
     GLuint id = arrays[i];
     if (id) {
       VertexArrayObjectMap::iterator it = vertex_array_objects_.find(id);
       if (it != vertex_array_objects_.end()) {
         if (bound_vertex_array_object_ == it->second) {
           bound_vertex_array_object_ = default_vertex_array_object_;
         }
         delete it->second;
         vertex_array_objects_.erase(it);
       }
     }
   }
 }

 bool VertexArrayObjectManager::BindVertexArray(GLuint array, bool* changed) {
   *changed = false;
   VertexArrayObject* vertex_array_object = default_vertex_array_object_;
   if (array != 0) {
     VertexArrayObjectMap::iterator it = vertex_array_objects_.find(array);
     if (it == vertex_array_objects_.end()) {
       return false;
     }
     vertex_array_object = it->second;
   }
   *changed = vertex_array_object != bound_vertex_array_object_;
   bound_vertex_array_object_ = vertex_array_object;
   return true;
 }

 bool VertexArrayObjectManager::HaveEnabledClientSideBuffers() const {
   return bound_vertex_array_object_->HaveEnabledClientSideBuffers();
 }

 void VertexArrayObjectManager::SetAttribEnable(GLuint index, bool enabled) {
   bound_vertex_array_object_->SetAttribEnable(index, enabled);
 }

 bool VertexArrayObjectManager::GetVertexAttrib(GLuint index,
                                                GLenum pname,
                                                uint32_t* param) {
   return bound_vertex_array_object_->GetVertexAttrib(index, pname, param);
 }

 bool VertexArrayObjectManager::GetAttribPointer(
     GLuint index, GLenum pname, void** ptr) const {
   return bound_vertex_array_object_->GetAttribPointer(index, pname, ptr);
 }

 bool VertexArrayObjectManager::SetAttribPointer(
     GLuint buffer_id,
     GLuint index,
     GLint size,
     GLenum type,
     GLboolean normalized,
     GLsizei stride,
     const void* ptr,
     GLboolean integer) {
   // Client side arrays are not allowed in vaos.
   if (buffer_id == 0 && !IsDefaultVAOBound()) {
     return false;
   }
   bound_vertex_array_object_->SetAttribPointer(
       buffer_id, index, size, type, normalized, stride, ptr, integer);
   return true;
 }

 void VertexArrayObjectManager::SetAttribDivisor(GLuint index, GLuint divisor) {
   bound_vertex_array_object_->SetAttribDivisor(index, divisor);
 }

 // Collects the data into the collection buffer and returns the number of
 // bytes collected.
 GLsizei VertexArrayObjectManager::CollectData(
     const void* data,
     GLsizei bytes_per_element,
     GLsizei real_stride,
     GLsizei num_elements) {
   GLsizei bytes_needed = bytes_per_element * num_elements;
   if (collection_buffer_size_ < bytes_needed) {
     collection_buffer_.reset(new int8_t[bytes_needed]);
     collection_buffer_size_ = bytes_needed;
   }
   const int8_t* src = static_cast<const int8_t*>(data);
   int8_t* dst = collection_buffer_.get();
   int8_t* end = dst + bytes_per_element * num_elements;
   for (; dst < end; src += real_stride, dst += bytes_per_element) {
     memcpy(dst, src, bytes_per_element);
   }
   return bytes_needed;
 }

 bool VertexArrayObjectManager::IsDefaultVAOBound() const {
   return bound_vertex_array_object_ == default_vertex_array_object_;
 }

 bool VertexArrayObjectManager::SupportsClientSideBuffers() {
   return support_client_side_arrays_ &&
          bound_vertex_array_object_->HaveEnabledClientSideBuffers();
 }

 // Returns true if buffers were setup.
 bool VertexArrayObjectManager::SetupSimulatedClientSideBuffers(
     const char* function_name,
     GLES2Implementation* gl,
     GLES2CmdHelper* gl_helper,
     GLsizei num_elements,
     GLsizei primcount,
     bool* simulated) {
   *simulated = false;
   if (!SupportsClientSideBuffers())
     return false;

   if (!IsDefaultVAOBound()) {
     gl->SetGLError(
         GL_INVALID_OPERATION, function_name,
         "client side arrays not allowed with vertex array object");
     return false;
   }
   *simulated = true;
   GLsizei total_size = 0;
   // Compute the size of the buffer we need.
   const VertexArrayObject::VertexAttribs& vertex_attribs =
       bound_vertex_array_object_->vertex_attribs();
   for (GLuint ii = 0; ii < vertex_attribs.size(); ++ii) {
     const VertexArrayObject::VertexAttrib& attrib = vertex_attribs[ii];
     if (attrib.IsClientSide() && attrib.enabled()) {
       size_t bytes_per_element =
           GLES2Util::GetGroupSizeForBufferType(attrib.size(), attrib.type());
       GLsizei elements = (primcount && attrib.divisor() > 0) ?
           ((primcount - 1) / attrib.divisor() + 1) : num_elements;
       total_size += RoundUpToMultipleOf4(bytes_per_element * elements);
     }
   }
   gl_helper->BindBuffer(GL_ARRAY_BUFFER, array_buffer_id_);
   array_buffer_offset_ = 0;
   if (total_size > array_buffer_size_) {
     gl->BufferDataHelper(GL_ARRAY_BUFFER, total_size, nullptr, GL_DYNAMIC_DRAW);
     array_buffer_size_ = total_size;
   }
   for (GLuint ii = 0; ii < vertex_attribs.size(); ++ii) {
     const VertexArrayObject::VertexAttrib& attrib = vertex_attribs[ii];
     if (attrib.IsClientSide() && attrib.enabled()) {
       size_t bytes_per_element =
           GLES2Util::GetGroupSizeForBufferType(attrib.size(), attrib.type());
       GLsizei real_stride = attrib.stride() ?
           attrib.stride() : static_cast<GLsizei>(bytes_per_element);
       GLsizei elements = (primcount && attrib.divisor() > 0) ?
           ((primcount - 1) / attrib.divisor() + 1) : num_elements;
       GLsizei bytes_collected = CollectData(
           attrib.pointer(), bytes_per_element, real_stride, elements);
       gl->BufferSubDataHelper(
           GL_ARRAY_BUFFER, array_buffer_offset_, bytes_collected,
           collection_buffer_.get());
       gl_helper->VertexAttribPointer(
           ii, attrib.size(), attrib.type(), attrib.normalized(), 0,
           array_buffer_offset_);
       array_buffer_offset_ += RoundUpToMultipleOf4(bytes_collected);
       DCHECK_LE(array_buffer_offset_, array_buffer_size_);
     }
   }
   return true;
 }

 // Copies in indices to the service and returns the highest index accessed + 1
 bool VertexArrayObjectManager::SetupSimulatedIndexAndClientSideBuffers(
     const char* function_name,
     GLES2Implementation* gl,
     GLES2CmdHelper* gl_helper,
     GLsizei count,
     GLenum type,
     GLsizei primcount,
     const void* indices,
     GLuint* offset,
     bool* simulated) {
   *simulated = false;
   *offset = ToGLuint(indices);
   if (!support_client_side_arrays_)
     return true;
   GLsizei num_elements = 0;
   if (bound_vertex_array_object_->bound_element_array_buffer() == 0) {
     *simulated = true;
     *offset = 0;
     GLsizei max_index = -1;
     switch (type) {
       case GL_UNSIGNED_BYTE: {
         const uint8_t* src = static_cast<const uint8_t*>(indices);
         for (GLsizei ii = 0; ii < count; ++ii) {
           if (src[ii] > max_index) {
             max_index = src[ii];
           }
         }
         break;
       }
       case GL_UNSIGNED_SHORT: {
         const uint16_t* src = static_cast<const uint16_t*>(indices);
         for (GLsizei ii = 0; ii < count; ++ii) {
           if (src[ii] > max_index) {
             max_index = src[ii];
           }
         }
         break;
       }
       case GL_UNSIGNED_INT: {
         uint32_t max_glsizei =
             static_cast<uint32_t>(std::numeric_limits<GLsizei>::max());
         const uint32_t* src = static_cast<const uint32_t*>(indices);
         for (GLsizei ii = 0; ii < count; ++ii) {
           // Other parts of the API use GLsizei (signed) to store limits.
           // As such, if we encounter a index that cannot be represented with
           // an unsigned int we need to flag it as an error here.
           if(src[ii] > max_glsizei) {
             gl->SetGLError(
                 GL_INVALID_OPERATION, function_name, "index too large.");
             return false;
           }
           GLsizei signed_index = static_cast<GLsizei>(src[ii]);
           if (signed_index > max_index) {
             max_index = signed_index;
           }
         }
         break;
       }
       default:
         break;
     }
     gl_helper->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_array_buffer_id_);
     GLsizei bytes_per_element = GLES2Util::GetGLTypeSizeForBuffers(type);
     GLsizei bytes_needed = bytes_per_element * count;
     if (bytes_needed > element_array_buffer_size_) {
       element_array_buffer_size_ = bytes_needed;
       gl->BufferDataHelper(GL_ELEMENT_ARRAY_BUFFER, bytes_needed, nullptr,
                            GL_DYNAMIC_DRAW);
     }
     gl->BufferSubDataHelper(
         GL_ELEMENT_ARRAY_BUFFER, 0, bytes_needed, indices);

     num_elements = max_index + 1;
   } else if (bound_vertex_array_object_->HaveEnabledClientSideBuffers()) {
     // Index buffer is GL buffer. Ask the service for the highest vertex
     // that will be accessed. Note: It doesn't matter if another context
     // changes the contents of any of the buffers. The service will still
     // validate the indices. We just need to know how much to copy across.
     num_elements = gl->GetMaxValueInBufferCHROMIUMHelper(
         bound_vertex_array_object_->bound_element_array_buffer(),
         count, type, ToGLuint(indices)) + 1;
   }

   bool simulated_client_side_buffers = false;
   SetupSimulatedClientSideBuffers(
       function_name, gl, gl_helper, num_elements, primcount,
       &simulated_client_side_buffers);
   *simulated = *simulated || simulated_client_side_buffers;
   return true;
 }

 }  // namespace gles2
 }  // namespace gpu
	// Copyright (c) 2012 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "gpu/command_buffer/client/vertex_array_object_manager.h"

	#include <stddef.h>
	#include <stdint.h>

	#include "base/logging.h"
	#include "base/macros.h"
	#include "gpu/command_buffer/client/gles2_cmd_helper.h"
	#include "gpu/command_buffer/client/gles2_implementation.h"
	#include "gpu/command_buffer/common/gles2_cmd_utils.h"

	namespace gpu {
	namespace gles2 {

	static GLsizei RoundUpToMultipleOf4(GLsizei size) {
	return (size + 3) & ~3;
	}

	// This class tracks VertexAttribPointers and helps emulate client side buffers.
	//
	// The way client side buffers work is we shadow all the Vertex Attribs so we
	// know which ones are pointing to client side buffers.
	//
	// At Draw time, for any attribs pointing to client side buffers we copy them
	// to a special VBO and reset the actual vertex attrib pointers to point to this
	// VBO.
	//
	// This also means we have to catch calls to query those values so that when
	// an attrib is a client side buffer we pass the info back the user expects.

	class GLES2_IMPL_EXPORT VertexArrayObject {
	public:
	// Info about Vertex Attributes. This is used to track what the user currently
	// has bound on each Vertex Attribute so we can simulate client side buffers
	// at glDrawXXX time.
	class VertexAttrib {
	public:
	VertexAttrib()
	: enabled_(false),
	buffer_id_(0),
	size_(4),
	type_(GL_FLOAT),
	normalized_(GL_FALSE),
	pointer_(nullptr),
	gl_stride_(0),
	divisor_(0),
	integer_(GL_FALSE) {}

	bool enabled() const {
	return enabled_;
	}

	void set_enabled(bool enabled) {
	enabled_ = enabled;
	}

	GLuint buffer_id() const {
	return buffer_id_;
	}

	void set_buffer_id(GLuint id) {
	buffer_id_ = id;
	}

	GLenum type() const {
	return type_;
	}

	GLint size() const {
	return size_;
	}

	GLsizei stride() const {
	return gl_stride_;
	}

	GLboolean normalized() const {
	return normalized_;
	}

	const GLvoid* pointer() const {
	return pointer_;
	}

	bool IsClientSide() const {
	return buffer_id_ == 0;
	}

	GLuint divisor() const {
	return divisor_;
	}

	GLboolean integer() const {
	return integer_;
	}

	void SetInfo(
	GLuint buffer_id,
	GLint size,
	GLenum type,
	GLboolean normalized,
	GLsizei gl_stride,
	const GLvoid* pointer,
	GLboolean integer) {
	buffer_id_ = buffer_id;
	size_ = size;
	type_ = type;
	normalized_ = normalized;
	gl_stride_ = gl_stride;
	pointer_ = pointer;
	integer_ = integer;
	}

	void SetDivisor(GLuint divisor) {
	divisor_ = divisor;
	}

	private:
	// Whether or not this attribute is enabled.
	bool enabled_;

	// The id of the buffer. 0 = client side buffer.
	GLuint buffer_id_;

	// Number of components (1, 2, 3, 4).
	GLint size_;

	// GL_BYTE, GL_FLOAT, etc. See glVertexAttribPointer.
	GLenum type_;

	// GL_TRUE or GL_FALSE
	GLboolean normalized_;

	// The pointer/offset into the buffer.
	const GLvoid* pointer_;

	// The stride that will be used to access the buffer. This is the bogus GL
	// stride where 0 = compute the stride based on size and type.
	GLsizei gl_stride_;

	// Divisor, for geometry instancing.
	GLuint divisor_;

	GLboolean integer_;
	};

	typedef std::vector<VertexAttrib> VertexAttribs;

	explicit VertexArrayObject(GLuint max_vertex_attribs);

	void UnbindBuffer(GLuint id);

	bool BindElementArray(GLuint id);

	bool HaveEnabledClientSideBuffers() const;

	void SetAttribEnable(GLuint index, bool enabled);

	void SetAttribPointer(
	GLuint buffer_id,
	GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride,
	const void* ptr, GLboolean integer);

	bool GetVertexAttrib(GLuint index, GLenum pname, uint32_t* param) const;

	void SetAttribDivisor(GLuint index, GLuint divisor);

	bool GetAttribPointer(GLuint index, GLenum pname, void** ptr) const;

	const VertexAttribs& vertex_attribs() const {
	return vertex_attribs_;
	}

	GLuint bound_element_array_buffer() const {
	return bound_element_array_buffer_id_;
	}

	private:
	const VertexAttrib* GetAttrib(GLuint index) const;

	int num_client_side_pointers_enabled_;

	// The currently bound element array buffer.
	GLuint bound_element_array_buffer_id_;

	VertexAttribs vertex_attribs_;

	DISALLOW_COPY_AND_ASSIGN(VertexArrayObject);
	};

	VertexArrayObject::VertexArrayObject(GLuint max_vertex_attribs)
	: num_client_side_pointers_enabled_(0),
	bound_element_array_buffer_id_(0) {
	vertex_attribs_.resize(max_vertex_attribs);
	}

	void VertexArrayObject::UnbindBuffer(GLuint id) {
	if (id == 0) {
	return;
	}
	for (size_t ii = 0; ii < vertex_attribs_.size(); ++ii) {
	VertexAttrib& attrib = vertex_attribs_[ii];
	if (attrib.buffer_id() == id) {
	attrib.set_buffer_id(0);
	if (attrib.enabled()) {
	++num_client_side_pointers_enabled_;
	}
	}
	}
	if (bound_element_array_buffer_id_ == id) {
	bound_element_array_buffer_id_ = 0;
	}
	}

	bool VertexArrayObject::BindElementArray(GLuint id) {
	if (id == bound_element_array_buffer_id_) {
	return false;
	}
	bound_element_array_buffer_id_ = id;
	return true;
	}
	bool VertexArrayObject::HaveEnabledClientSideBuffers() const {
	return num_client_side_pointers_enabled_ > 0;
	}

	void VertexArrayObject::SetAttribEnable(GLuint index, bool enabled) {
	if (index < vertex_attribs_.size()) {
	VertexAttrib& attrib = vertex_attribs_[index];
	if (attrib.enabled() != enabled) {
	if (attrib.IsClientSide()) {
	num_client_side_pointers_enabled_ += enabled ? 1 : -1;
	DCHECK_GE(num_client_side_pointers_enabled_, 0);
	}
	attrib.set_enabled(enabled);
	}
	}
	}

	void VertexArrayObject::SetAttribPointer(
	GLuint buffer_id,
	GLuint index,
	GLint size,
	GLenum type,
	GLboolean normalized,
	GLsizei stride,
	const void* ptr,
	GLboolean integer) {
	if (index < vertex_attribs_.size()) {
	VertexAttrib& attrib = vertex_attribs_[index];
	if (attrib.IsClientSide() && attrib.enabled()) {
	--num_client_side_pointers_enabled_;
	DCHECK_GE(num_client_side_pointers_enabled_, 0);
	}

	attrib.SetInfo(buffer_id, size, type, normalized, stride, ptr, integer);

	if (attrib.IsClientSide() && attrib.enabled()) {
	++num_client_side_pointers_enabled_;
	}
	}
	}

	bool VertexArrayObject::GetVertexAttrib(GLuint index,
	GLenum pname,
	uint32_t* param) const {
	const VertexAttrib* attrib = GetAttrib(index);
	if (!attrib) {
	return false;
	}

	switch (pname) {
	case GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING:
	*param = attrib->buffer_id();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_ENABLED:
	*param = attrib->enabled();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_SIZE:
	*param = attrib->size();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_STRIDE:
	*param = attrib->stride();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_TYPE:
	*param = attrib->type();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_NORMALIZED:
	*param = attrib->normalized();
	break;
	case GL_VERTEX_ATTRIB_ARRAY_INTEGER:
	*param = attrib->integer();
	break;
	default:
	return false; // pass through to service side.
	}
	return true;
	}

	void VertexArrayObject::SetAttribDivisor(GLuint index, GLuint divisor) {
	if (index < vertex_attribs_.size()) {
	VertexAttrib& attrib = vertex_attribs_[index];
	attrib.SetDivisor(divisor);
	}
	}

	// Gets the Attrib pointer for an attrib but only if it's a client side
	// pointer. Returns true if it got the pointer.
	bool VertexArrayObject::GetAttribPointer(
	GLuint index, GLenum pname, void** ptr) const {
	const VertexAttrib* attrib = GetAttrib(index);
	if (attrib && pname == GL_VERTEX_ATTRIB_ARRAY_POINTER) {
	ptr = const_cast<void>(attrib->pointer());
	return true;
	}
	return false;
	}

	// Gets an attrib if it's in range and it's client side.
	const VertexArrayObject::VertexAttrib* VertexArrayObject::GetAttrib(
	GLuint index) const {
	if (index < vertex_attribs_.size()) {
	const VertexAttrib* attrib = &vertex_attribs_[index];
	return attrib;
	}
	return nullptr;
	}

	VertexArrayObjectManager::VertexArrayObjectManager(
	GLuint max_vertex_attribs,
	GLuint array_buffer_id,
	GLuint element_array_buffer_id,
	bool support_client_side_arrays)
	: max_vertex_attribs_(max_vertex_attribs),
	array_buffer_id_(array_buffer_id),
	array_buffer_size_(0),
	array_buffer_offset_(0),
	element_array_buffer_id_(element_array_buffer_id),
	element_array_buffer_size_(0),
	collection_buffer_size_(0),
	default_vertex_array_object_(new VertexArrayObject(max_vertex_attribs)),
	bound_vertex_array_object_(default_vertex_array_object_),
	support_client_side_arrays_(support_client_side_arrays) {
	}

	VertexArrayObjectManager::~VertexArrayObjectManager() {
	for (VertexArrayObjectMap::iterator it = vertex_array_objects_.begin();
	it != vertex_array_objects_.end(); ++it) {
	delete it->second;
	}
	delete default_vertex_array_object_;
	}

	bool VertexArrayObjectManager::IsReservedId(GLuint id) const {
	return (id != 0 &&
	(id == array_buffer_id_ \|\| id == element_array_buffer_id_));
	}

	GLuint VertexArrayObjectManager::bound_element_array_buffer() const {
	return bound_vertex_array_object_->bound_element_array_buffer();
	}

	void VertexArrayObjectManager::UnbindBuffer(GLuint id) {
	bound_vertex_array_object_->UnbindBuffer(id);
	}

	bool VertexArrayObjectManager::BindElementArray(GLuint id) {
	return bound_vertex_array_object_->BindElementArray(id);
	}

	void VertexArrayObjectManager::GenVertexArrays(
	GLsizei n, const GLuint* arrays) {
	DCHECK_GE(n, 0);
	for (GLsizei i = 0; i < n; ++i) {
	std::pair<VertexArrayObjectMap::iterator, bool> result =
	vertex_array_objects_.insert(std::make_pair(
	arrays[i], new VertexArrayObject(max_vertex_attribs_)));
	DCHECK(result.second);
	}
	}

	void VertexArrayObjectManager::DeleteVertexArrays(
	GLsizei n, const GLuint* arrays) {
	DCHECK_GE(n, 0);
	for (GLsizei i = 0; i < n; ++i) {
	GLuint id = arrays[i];
	if (id) {
	VertexArrayObjectMap::iterator it = vertex_array_objects_.find(id);
	if (it != vertex_array_objects_.end()) {
	if (bound_vertex_array_object_ == it->second) {
	bound_vertex_array_object_ = default_vertex_array_object_;
	}
	delete it->second;
	vertex_array_objects_.erase(it);
	}
	}
	}
	}

	bool VertexArrayObjectManager::BindVertexArray(GLuint array, bool* changed) {
	*changed = false;
	VertexArrayObject* vertex_array_object = default_vertex_array_object_;
	if (array != 0) {
	VertexArrayObjectMap::iterator it = vertex_array_objects_.find(array);
	if (it == vertex_array_objects_.end()) {
	return false;
	}
	vertex_array_object = it->second;
	}
	*changed = vertex_array_object != bound_vertex_array_object_;
	bound_vertex_array_object_ = vertex_array_object;
	return true;
	}

	bool VertexArrayObjectManager::HaveEnabledClientSideBuffers() const {
	return bound_vertex_array_object_->HaveEnabledClientSideBuffers();
	}

	void VertexArrayObjectManager::SetAttribEnable(GLuint index, bool enabled) {
	bound_vertex_array_object_->SetAttribEnable(index, enabled);
	}

	bool VertexArrayObjectManager::GetVertexAttrib(GLuint index,
	GLenum pname,
	uint32_t* param) {
	return bound_vertex_array_object_->GetVertexAttrib(index, pname, param);
	}

	bool VertexArrayObjectManager::GetAttribPointer(
	GLuint index, GLenum pname, void** ptr) const {
	return bound_vertex_array_object_->GetAttribPointer(index, pname, ptr);
	}

	bool VertexArrayObjectManager::SetAttribPointer(
	GLuint buffer_id,
	GLuint index,
	GLint size,
	GLenum type,
	GLboolean normalized,
	GLsizei stride,
	const void* ptr,
	GLboolean integer) {
	// Client side arrays are not allowed in vaos.
	if (buffer_id == 0 && !IsDefaultVAOBound()) {
	return false;
	}
	bound_vertex_array_object_->SetAttribPointer(
	buffer_id, index, size, type, normalized, stride, ptr, integer);
	return true;
	}

	void VertexArrayObjectManager::SetAttribDivisor(GLuint index, GLuint divisor) {
	bound_vertex_array_object_->SetAttribDivisor(index, divisor);
	}

	// Collects the data into the collection buffer and returns the number of
	// bytes collected.
	GLsizei VertexArrayObjectManager::CollectData(
	const void* data,
	GLsizei bytes_per_element,
	GLsizei real_stride,
	GLsizei num_elements) {
	GLsizei bytes_needed = bytes_per_element * num_elements;
	if (collection_buffer_size_ < bytes_needed) {
	collection_buffer_.reset(new int8_t[bytes_needed]);
	collection_buffer_size_ = bytes_needed;
	}
	const int8_t* src = static_cast<const int8_t*>(data);
	int8_t* dst = collection_buffer_.get();
	int8_t* end = dst + bytes_per_element * num_elements;
	for (; dst < end; src += real_stride, dst += bytes_per_element) {
	memcpy(dst, src, bytes_per_element);
	}
	return bytes_needed;
	}

	bool VertexArrayObjectManager::IsDefaultVAOBound() const {
	return bound_vertex_array_object_ == default_vertex_array_object_;
	}

	bool VertexArrayObjectManager::SupportsClientSideBuffers() {
	return support_client_side_arrays_ &&
	bound_vertex_array_object_->HaveEnabledClientSideBuffers();
	}

	// Returns true if buffers were setup.
	bool VertexArrayObjectManager::SetupSimulatedClientSideBuffers(
	const char* function_name,
	GLES2Implementation* gl,
	GLES2CmdHelper* gl_helper,
	GLsizei num_elements,
	GLsizei primcount,
	bool* simulated) {
	*simulated = false;
	if (!SupportsClientSideBuffers())
	return false;

	if (!IsDefaultVAOBound()) {
	gl->SetGLError(
	GL_INVALID_OPERATION, function_name,
	"client side arrays not allowed with vertex array object");
	return false;
	}
	*simulated = true;
	GLsizei total_size = 0;
	// Compute the size of the buffer we need.
	const VertexArrayObject::VertexAttribs& vertex_attribs =
	bound_vertex_array_object_->vertex_attribs();
	for (GLuint ii = 0; ii < vertex_attribs.size(); ++ii) {
	const VertexArrayObject::VertexAttrib& attrib = vertex_attribs[ii];
	if (attrib.IsClientSide() && attrib.enabled()) {
	size_t bytes_per_element =
	GLES2Util::GetGroupSizeForBufferType(attrib.size(), attrib.type());
	GLsizei elements = (primcount && attrib.divisor() > 0) ?
	((primcount - 1) / attrib.divisor() + 1) : num_elements;
	total_size += RoundUpToMultipleOf4(bytes_per_element * elements);
	}
	}
	gl_helper->BindBuffer(GL_ARRAY_BUFFER, array_buffer_id_);
	array_buffer_offset_ = 0;
	if (total_size > array_buffer_size_) {
	gl->BufferDataHelper(GL_ARRAY_BUFFER, total_size, nullptr, GL_DYNAMIC_DRAW);
	array_buffer_size_ = total_size;
	}
	for (GLuint ii = 0; ii < vertex_attribs.size(); ++ii) {
	const VertexArrayObject::VertexAttrib& attrib = vertex_attribs[ii];
	if (attrib.IsClientSide() && attrib.enabled()) {
	size_t bytes_per_element =
	GLES2Util::GetGroupSizeForBufferType(attrib.size(), attrib.type());
	GLsizei real_stride = attrib.stride() ?
	attrib.stride() : static_cast<GLsizei>(bytes_per_element);
	GLsizei elements = (primcount && attrib.divisor() > 0) ?
	((primcount - 1) / attrib.divisor() + 1) : num_elements;
	GLsizei bytes_collected = CollectData(
	attrib.pointer(), bytes_per_element, real_stride, elements);
	gl->BufferSubDataHelper(
	GL_ARRAY_BUFFER, array_buffer_offset_, bytes_collected,
	collection_buffer_.get());
	gl_helper->VertexAttribPointer(
	ii, attrib.size(), attrib.type(), attrib.normalized(), 0,
	array_buffer_offset_);
	array_buffer_offset_ += RoundUpToMultipleOf4(bytes_collected);
	DCHECK_LE(array_buffer_offset_, array_buffer_size_);
	}
	}
	return true;
	}

	// Copies in indices to the service and returns the highest index accessed + 1
	bool VertexArrayObjectManager::SetupSimulatedIndexAndClientSideBuffers(
	const char* function_name,
	GLES2Implementation* gl,
	GLES2CmdHelper* gl_helper,
	GLsizei count,
	GLenum type,
	GLsizei primcount,
	const void* indices,
	GLuint* offset,
	bool* simulated) {
	*simulated = false;
	*offset = ToGLuint(indices);
	if (!support_client_side_arrays_)
	return true;
	GLsizei num_elements = 0;
	if (bound_vertex_array_object_->bound_element_array_buffer() == 0) {
	*simulated = true;
	*offset = 0;
	GLsizei max_index = -1;
	switch (type) {
	case GL_UNSIGNED_BYTE: {
	const uint8_t* src = static_cast<const uint8_t*>(indices);
	for (GLsizei ii = 0; ii < count; ++ii) {
	if (src[ii] > max_index) {
	max_index = src[ii];
	}
	}
	break;
	}
	case GL_UNSIGNED_SHORT: {
	const uint16_t* src = static_cast<const uint16_t*>(indices);
	for (GLsizei ii = 0; ii < count; ++ii) {
	if (src[ii] > max_index) {
	max_index = src[ii];
	}
	}
	break;
	}
	case GL_UNSIGNED_INT: {
	uint32_t max_glsizei =
	static_cast<uint32_t>(std::numeric_limits<GLsizei>::max());
	const uint32_t* src = static_cast<const uint32_t*>(indices);
	for (GLsizei ii = 0; ii < count; ++ii) {
	// Other parts of the API use GLsizei (signed) to store limits.
	// As such, if we encounter a index that cannot be represented with
	// an unsigned int we need to flag it as an error here.
	if(src[ii] > max_glsizei) {
	gl->SetGLError(
	GL_INVALID_OPERATION, function_name, "index too large.");
	return false;
	}
	GLsizei signed_index = static_cast<GLsizei>(src[ii]);
	if (signed_index > max_index) {
	max_index = signed_index;
	}
	}
	break;
	}
	default:
	break;
	}
	gl_helper->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_array_buffer_id_);
	GLsizei bytes_per_element = GLES2Util::GetGLTypeSizeForBuffers(type);
	GLsizei bytes_needed = bytes_per_element * count;
	if (bytes_needed > element_array_buffer_size_) {
	element_array_buffer_size_ = bytes_needed;
	gl->BufferDataHelper(GL_ELEMENT_ARRAY_BUFFER, bytes_needed, nullptr,
	GL_DYNAMIC_DRAW);
	}
	gl->BufferSubDataHelper(
	GL_ELEMENT_ARRAY_BUFFER, 0, bytes_needed, indices);

	num_elements = max_index + 1;
	} else if (bound_vertex_array_object_->HaveEnabledClientSideBuffers()) {
	// Index buffer is GL buffer. Ask the service for the highest vertex
	// that will be accessed. Note: It doesn't matter if another context
	// changes the contents of any of the buffers. The service will still
	// validate the indices. We just need to know how much to copy across.
	num_elements = gl->GetMaxValueInBufferCHROMIUMHelper(
	bound_vertex_array_object_->bound_element_array_buffer(),
	count, type, ToGLuint(indices)) + 1;
	}

	bool simulated_client_side_buffers = false;
	SetupSimulatedClientSideBuffers(
	function_name, gl, gl_helper, num_elements, primcount,
	&simulated_client_side_buffers);
	simulated = simulated \|\| simulated_client_side_buffers;
	return true;
	}

	} // namespace gles2
	} // namespace gpu